You earn on RewardEarn by completing offers. Open the Earn page, pick an offer, and complete the steps it lists, your reward is added to your Total Wallet Balance, which you withdraw from the Cashout page.
Every offer shows its reward up front in Rebux (R$), RewardEarn's main currency displayed in whatever currency you've selected. Two counters on the Earn page track your progress:
Pending Rewards — earnings that are credited but still being confirmed by the advertiser.
Completed Offers — the number of offers you've finished.
Your activity also appears under Recent Activity as you earn.